In the transmission of light energy, numerous instances arise which call for a lessening, if not an elimination, of back reflection of transmitted energy along the transmission axis, for example, from energy coupling interfaces. Such reflections of energy into the energy output axis of a laser, as may arise at the coupling interface of the laser output fiber and another fiber, can intrude substantially upon the intended laser output energy and performance.
Energy reflections at a coupling interface between fiber ends can be eliminated by: (1) bringing the light-carrying fiber cores into physical contact; (2) introducing optical matching fluid or gel between the fibers; or (3) optically "coating" non-contacting fiber ends. Each of these techniques carries serious disadvantages in the manufacture and/or use of practical optical fiber couplers.
Predictability and consistency in such optical fiber connector performance is paramount to overall system design. While limited connector loss of constant measure is tolerable in system design, connector abberations due to variations in reflectivity of transmitted energy back along the energy transmission axis, for instance, back along the laser output fiber above, are not tolerable to the system designer.
In applicant's view, the present state of the art in the area under discussion falls short of the current industry requirements.